Solution of sodium aluminate.



NITED STATES PATENT OFFICE.

HOWARD srnncn AND mnomasaonn IRELAND CRAIG, or

MANCHESTER, ENGLAND,

ASSIGNQRS TO COMPANY 0]? PETER SPENCE & SONS LIMITED, 01? MANCHESTER,

Patented Oct. 19, 1915.

ENGLAND.

' SOLUTION 0F SQDIUM ALUMINATE.

1,157,436. I Specification of Letters Patent. NoDrawing.

To all whom it may concern:

Be it known that we, HOWARD SPENCE and THOMAS J OHN IRELAND CRAIG, bothsub- The employment of solutions of sodium aluminate in the arts ishindered by their instability on keeping. It is known that thesesolutionsare increasingly stable with an increasing ratio of sodium toaluminum and that strong solutions are more stable than weaker ones. Foruse in the arts it is desirable to employ solutions with as low a ratioas practicable of sodium to aluminum, 0. 9., a molecular ratio of about1.25 Na,O to 1 A1 0 is advantageous. Such solutions however, except atvery high concentrations,

' e..g. at specific gravltles of about' li5'to 1.6,

are very unstable. Thus at specific gravities of about 1.15 to 1.25 suchsolutions in about a day show considerable decomposition byspontaneously precipitating alumina hydroxid,their effective employmentunder technical conditions being thus 'materially limited.

According to this invention a solution of would otherwise take place insuch solution.

Such substance must also possess the quality of not prejudiciallyaffecting the solution for the purpose for whichit is to be used in thearts. Substances suitable for use in will be jiereinafter included in areference to a sub- Application filed August 18, 1914. Serial No.857,313.

stance which inhibits the spontaneous pretipitation of alumina hydroxid.Examples j f such substances are sugar, dextrin, starch or othersuitable carbo-hydrates, glycerin, phenols, gelatin or other colloidalsubstances, or saccharates, tartrates,

irganic salts.

The following is an example of the proluction of a stable solution ofsodium aluminate according to this invention. A solution of sodiumaluminate having a low ratio or other suitable of soda toalumina and aspecific gravity of about 1.4.5 to 1.55 in the cold is treated at 100 C.with a proportion ofsugar equal to about one half to one and a half percent on -the weight of the solution, and the heat maintained for abouttwo hours. The solution, after the treatment is completed. will be freeor substantially free from any liability to spontaneously precipitatealumina hydroxid, and is, consequently, of high stability. It can bediluted for use under ordinary' conditions without risk of materialprecipitation of alumina hydroxid in the dilute solution for a prolongedperiod.

. What we claim is A solution of sodium aluminate containing an addedsubstance which inhibits the spontaneous precipitation of aluminahydroxid and is not prejudicial to the solution for the purpose forwhich it is to be used, substantially as set forth.

In witness whereof we vhave hereunto set our hands in the presence oftwo subscribing witnesses.

' HOWARD SPENCE.

THOMAS JOHN IRELAND CRAIG. Witnesses:

ERNALD SIMPSON MosnLEY, FRANK ATLnYs.

